PCB Design
Due to the hardware reliability issues of building circuits on protoboards, an effort to produce PCBs to our needs. This will allow for much improved reliability, smaller circuits, as well as provide some form of documentation for future use. PBCs have great potential, the redesigned rs232 converter is less than half the size of the protoboard model. Care must be taken in design as mistakes are more costly in terms of both money and time. Eagle Eagle is a free to use pcb design tool. The pro version offers the ability to make larger boards but we do not need that at the moment. To use Eagle, start by making a new project, and open a new schematic. Click add part to search and add parts from the library. The part does not have to be an exact match as long as the hole dimensions are the same and there is enough spacing to fit the part. Once the schematic is made click on board buttom on the top left. This will bring up the PCB design board. Move the components into the desired positions. Press auto when satisfied. If you need to rework the design press the RipUp folled by go (the green trafficlight). Also if the board design not good enough, look at the options on routing direction in the auto mode. After routing be sure to test the board layout by running drc, located just under auto. This tool checks to make sure there are no conflicts and that the tolerance is sufficant on everything. Make sure to set limits to 10mils instead of 8 as this increases the reliability of the system. If there is a conflict rerun the auto-router with different settings or manually change the circuit layout. Always re-run drc after every modification, and be sure to have the board looked over by another person before making the gerber files. Pay attention to any dimensional discrepancies between a part from the library and real life. For example, the headers being used require and additional 25mils on the sides and 75 mils on the top and bottom in order to fit. If unsure of the sizing leave extra space, do not try and overload a circuitboard if it means that something wont fit. Further info can be found : http://myhome.spu.edu/bolding/EE4211/EagleTutorial4.htm Gerber Files The design is complete, but many manufacturers cannot use Eagle files to generate PCBs, instead they use the industrial standard gerber files, and NC drill files. To do this, press the CAM button at the top left. Go to file->open->job... and choose gerber274x.cam. Press process job, this will generate the Gerber files for the top and bottom copper, the silkscreens and the soldermasks, as was the drill file. Do not mess with the settings in the cam file unless you know what you are doing as this will change what layers will show up in the generated gerber file. Once the file are generated, open Viewplot, and select load files, choose all the gerber files from your project, they will end in .GTL .GBL .GBO .GTO .GTS .GBS. The drill file will be in a text file. Make sure to choose 24 and leading zero suppression, as well as dimmensions in mm. Verify that the drawing is correct and that everything lines up as intended. Send this file off to the manufacturer, you may need to combine them into a zip file for easier packaging. Ordering Currently we are using APCircuits. Minimum order is 2 and price is about 25 per board including shipping. They are alberta based and offer a fairly good turnaround time. http://www.apcircuits.com/ Backups can be made at BatchPCB, they are very cheap, 10 per board plus shipping and no limits on number of boards, but have a turnaround time of about 2 weeks or more. http://batchpcb.com/index.php/Faq#What is this place If emergency work is needed to be done use the PCB making in the prototyping lab, it is 50 per board. Category:Hardware